Use of a new microcomputer-based instrumentation system to record and analyze current waveforms produced by applying square voltage pulses of 0.5-3.5 V to the skin revealed that peak currents are considerably higher, and corresponding pre-polarization resistance values considerably lower, than previously supposed. However, in keeping with previous observations, we confirmed that the skin is an Ohm's Law conductor in its pre-polarization state and that the pre-polarization resistance of the skin is resolvable into two components, a localized resistance beneath each electrode and a non-localized (body core) resistance. In addition, a three-electrode method was devised to measure the localized resistance at any selected location (target site). Simple equivalent circuit simulations of the initial section of current waveforms are used to assess the degree of instrument-related peak current underestimation inherent even in this system. This preliminary study indicates the need for reassessment of the roles played by the various body tissues, particularly the epidermis, in determining the pre-polarization electrical character of the skin.

full text: http://www.cihs.edu/wordpress/wp-content/uploads/2012/01/Pre-Polarization-Resistance-from-Psychophysiology.pdf

Pre-Polarization Resistance of the Skin as Determined by the Single Square Voltage Pulse Method